Officials say the fire tore through Spartan Sales Co. at 15 Evans Terminal just before 6:30 a.m.
Heavy smoke spewed from the 30,000 square-foot structure, as firefighters used tower ladders to put water on the fire.
Eyewitness News is told several explosions were reported inside the building, which houses construction supplies. Nearly 100 firefighters battled the blaze, but none were injured.
The inferno drew firefighters from nine towns.
